Search will be continued for metabolic correlates of slow rhythmic potentials in longitudinal muscle of small intestine of cat. Specifics of the coupling between the two muscle layers and the nature of amplification of slow waves by circular fibers will be detailed. Analysis of the different voltage-current relations of longitudinal and circular muscle will be made in terms of ionic properties. Spiking mechanisms will be examined for the possibility of two types of calcium conductance change, for the effects of calcium of potassium permeability and for synergism between calcium and sodium. The latter topic will also be pursued by continued measurements of efflux of radioactive calcium, particularly as affected by sodium. Electrical properties of muscle fibers in experimental ileus will be measured. In a study of gastrointestinal muscle of lower vertebrates the generality of mechanisms of rhythmicity will be investigated and better models sought.